This invention relates to high intensity discharge devices; and more particularly to fills for use in high intensity discharge devices.
The search for more efficient white light sources is continually driven by engergy concerns. In the past, light sources most commonly used in the home environment have been incadescant bulbs, which are energy inefficient. Recently, use of the more efficient fluorescent lamp has increased in the home environment. Although metal halide arc discharge sources are good white light emitters, these light sources are not generally used in the home environment. Metal halide arc discharges are, however, used extensively in industrial settings. More specifically, high pressure electric discharge lamps containing mercury with sodium and scandium iodides are commercially available and have received wide use in such settings. These sources have high efficacy (80 LPW), good color rendering (color rendition index, CRI=65), and reasonably low color temperature (T=4700). For metal halide arc discharges to be used for general illumination, especially in residential applications, the devices should have comparable efficacy but a warmer color temperature which produces more desirable skin tones.
An example of a high intensity discharge device with improved color is found in U.S. Pat. No. 3,720,855, issued to Gardner et al. on Mar. 13, 1973, which describes an electric discharge lamp containing a fill which includes at least one oxytrihalide of a Group VB element, the partial pressure of the oxytrihalide being in the range of from about 0.001 torr to about 200 torr. However, lamps containing the fill described in the Gardner patent, whether electroded or electrodeless, suffer from short lifetimes due to instability of the discharge.